Make "gaussian laser beam" (object with variable radial emission profile)
Here is a node setup that approximates the Gaussian beam.


normalize the coordinates of the object by division on the dimensions
subdivide the radial dimensions "in this case Y and Z" on the beam length "X" 
feed  Y Z into a Gaussian function to create the redial gradient
the longitude gradient is simple (beam length-X)




Coordinates node group


Gaussian function node group

The A input in the Gaussian function group controls the amplitude of the Gaussian function.
S_y and S_z control the Y and Z spread.

simple render :

another render :


.blend file
YA render